Much of the East and Midwest, meanwhile, will be stuck with temperatures in the high 80s and even low 90s for several days. By contrast, Central New York will see highs mostly in the high 70s into the weekend.

Why are we getting a reprieve? Cold air now sitting over northern Canada will sink south Wednesday.

"There's an air mass up around the Hudson Bay area that will push south and put an end to the heat - if not by Wednesday, then by Wednesday night," said AccuWeather.com meteorologist Tom Kines.

Eastern cities including Pittsburgh, Pennsylvania and Philadelphia are likely to hit 90 degrees today for the first time this year, AccuWeather said. Washington, D.C., could have three plus-90 degree days in a row.

Syracuse has had one 90-degree this year, on June 2. Today will seem just as hot, though, because the humidity will be about 45 percent this afternoon. On June 2, it was about 35 percent.

Today's high will about 10 degrees above the average mid-June high of 77 degrees. We could also see some strong thunderstorms.

After today, we'll see a high Wednesday of 83 with some thunderstorms, and then highs in the high 70s all the way through Sunday.